1. Field of the Invention
The invention relates generally to safety inspections and requalification of transport arrangements. More specifically, the invention relates to a method and arrangement for the inspection and requalification of tank cars and the like type of cargo carrying vehicles adapted to transport commodities including regulated and un-regulated materials.
2. Description of the Related Art
Until recently, the inspection process for Department of Transportation (DOT) specified rail-borne tank cars transporting either hazardous or non-hazardous commodities was relatively simple. The inspections consisted of hydrostatically testing the tank-car, typically performed on a 10-year interval. However, this conventional testing methodology only detected through-wall cracks and was insufficient to detect cracks that were slightly less than a through-wall crack. Consequently, some tanks failed shortly after being hydro-tested. HM-201, later codified in 49 C.F.R. Subpart F §§180.500 et al. (hereinafter 49 C.F.R. §180) was developed to provide a more comprehensive inspection process using a variety of non-destructive testing (NDT) methods. Namely, 49 C.F.R. §180 includes a (1) Visual Inspection, (2) Structural Inspection, (3) Service Life Shell Thickness Inspection, (4) Safety System Inspection, (5) Lining/Coating Inspection, and (6) Leakage Pressure Test.
As set forth in 49 C.F.R. §180.509, the visual inspection entails external and internal inspection of (1) the tank shell interior and exterior; (2) piping, valves, fittings, & gaskets; (3) missing or loose elements, (4) all closures and protective housings; (5) excess flow valves (when applicable), and (6) all the required markings on the Tank Car. The Structural Inspection requires, at a minimum, inspection of all transverse fillet welds greater than 0.25 inches within 4 feet of the bottom longitudinal centerline; the termination of longitudinal fillet welds greater than 4 feet from the bottom longitudinal center line; and all tank shell butt welds within 2 feet of the bottom longitudinal center line. These structural inspections may be performed by dye penetrant, radiography, magnetic particle, ultrasonic, or optically-aided tests. The Service Life Shell Thickness Inspection requires inspection of the thickness of the tank car shell, heads, sumps, domes, and nozzles with a device accurate to within +/−0.002 inches. A tank car with a shell thickness below a required minimum thickness (set forth in 49 C.F.R. §§179.100-6 and 179.101-1) may be permitted to continue operation under 49 C.F.R. §180.509 if certain additional criteria are met, set forth therein.
The Safety System Inspection requires, at a minimum, inspect the thermal protection systems, tank head puncture resistance systems, coupler vertical restraint systems, and systems used to protect discontinuities (i.e., skid protection and protective housings) to ensure their integrity. It also requires removing the safety relief device from the Tank Car and testing of the device with air or another gas to ensure that it conforms to the start-to-discharge pressure for the specification or hazardous material. The Lining and Coating Inspection requires, at a minimum, inspection of the lining or coating installed on the tank car according to the inspection interval, test technique, and acceptance criteria established by the owner of the lining or coating. Finally, 49 C.F.R. §180.509 requires a Leakage Pressure Test after re-assembly of a tank car or service equipment, wherein a tank car facility must perform a leak test on the tank or service equipment to detect leakage, if any, between manway covers, cover plates, and service equipment.
These inspections are generally to be performed on an inspection interval set in accord with the type of tank car and the transported commodity. For cars transporting materials not corrosive to the tank, the inspections above are to be performed at a maximum of every 10 years for the tank and service equipment. For non-lined or non-coated tank cars transporting materials corrosive to the tank, an interval (i) may be set in accord with the difference between the actual thickness and the allowable minimum thickness divided by the corrosion rate of the transported commodity, per year. In cases where a lining or coating is applied to protect the tank shell from the lading, the owner of the lining is charged to determine the periodic inspection interval, test technique, and acceptance criteria for the lining or coating. 49 C.F.R. §180 has since been supplemented by Alternative Tank Car Requalification Program, Appendix B to DOT-E 12095 (hereinafter “DOT 12095”). DOT 12095 is substantially similar to 49 C.F.R. §180; however, it eliminates the dependence of the allowable minimum thickness on corrosion and, instead, sets forth a list of forty corrosive materials in Attachment A thereto and, for non-lined and non-coated tanks, ties the tank shell thickness qualification frequencies to both the transport of a material listed in Attachment A and the measured remaining shell and head thickness. Thus, the revised standard provides more definite criteria for determination of tank thickness in the absence of corrosion rates required by the formula of 49 C.F.R. §180. However, DOT 12095 requires that owner's follow the alternative program provided therein to develop written procedures to ensure tank car safety, as required by 49 C.F.R §179.7(d), but places the burden, as 49 C.F.R. §180, on the owner's to develop qualification programs for each tank car, or a fleet of tank cars, identifying where to inspect, how to inspect, and the inspection criteria to complement the minimal guidance provided therein.
Other inspection guidelines have been issued to improve tank car safety. Rule 88.B.2 issued by the Federal Railroad Administration (FRA) requires, every five years, a “thorough inspection must be performed and repairs where necessary be made to the following: (1) Body bolsters and center plates; (2) Center sills; (3) Crossbearers; (4) Crossties; (5) Draft systems and components; (6) End sills; (7) Side sills; (8) Trucks; and (9) Car jackets. In addition, various AAR (Association of American Railroads) circulars prescribe inspection intervals and guidelines for stub sill tank cars based on a damage tolerance analysis (DTA) philosophy or at a default inspection interval of five years or 75,000 miles. However, the AAR Tank Car Stub Sill Inspection Program, requests owners to develop written procedures that encompass: (1) Identifying structurally significant components and welds; (2) a means of access to these components and welds, including removal of the jacket, insulation, or thermal coating, if required; (3) inspection techniques to ensure the detection of damage; and (4) proper identification, measurement, and reporting of cracks by line item on the required inspection report form (AAR Form SSIP).
Thus, to improve the level of safety and security with which hazardous materials can be transported from one place to another, it has been proposed to increase the requirements for the qualification and maintenance of tank cars which are used to transport such materials along the rail systems of the country. However, these requirements impose a significant burden on the tank car and tank car lining owners to develop and implement procedures to provide the mandated level of safety and ensure this level of safety between inspections of the tank cars, tank car linings, and appurtenant equipment. The actual manner in which the tests may be satisfactorily carried out have not been defined in terms sufficiently specific to detail just what type of tests are required and how these tests need to be actually carried out to ensure that all of the features and structures which tend to be at high risk, are examined in a proper manner. In other words, a worker skilled in the art of inspecting tank cars, even with many years of experience, would need guidance as to the totality of how many parameters to test for, how many sites need to be examined and with what equipment should the tests be implemented.
A further shortcoming in the art is that there has been no concerted effort to record the results which are derived and to compile this data in a form which will enable the status of each of the vessels, tanks bogies and the like which are inspected, to be tracked over a period of time and enable a relatively accurate prediction as to the status of each of a fleet of units.
Further, the revised inspection requirements impose additional and varied inspection cycles, including for example, unique test cycles for lined cars in corrosive service versus unlined cars in corrosive service. The cycle for unlined cars in corrosive service is determined by rate of corrosion versus remaining allowable shell thickness, whereas the cycle for lined cars in corrosive service is set to 10 years. However, for lined cars in corrosive service the service equipment must be inspected every five years, thus requiring the tank car to be brought in for inspection every five years. Additionally,there are two separate required stub sill inspections—SSIP and Rule 88.B.2, which may run on staggered inspection cycles. Therefore, for a given tank car, an SSIP inspection may be required and performed in year 1, a Rule 88.B.2 inspection may be required and performed in the following year, and a HM-201 inspection may be required and performed in year 3, the staggered sequence to be continued into future years.
Historically, the industry has deferred tank car inspections and maintenance as long as possible to minimize and defer immediate expenditures. Conventional wisdom, therefore, permits cars to be brought into a facility on multiple occasions over a 10 year period. Although in one respect this minimizes costs for a particular, it is inefficient over longer time periods. Further,the increased non-destructive testing mandated by 49 C.F.R. §180 is likely to increase backlogs at test facilities. The average time a car remains in the shop facility is approximately 30 days. In accord with common business practices, the tank car will “come off of lease” after five days of inactivity and rental credits are issued to the entity leasing the car since the entity does not want to be liable for periods of inactivity of the leased tank car. The increased inspection requirements will necessarily entail longer periods of tank car inactivity in the facility and increased backlogs, further resulting in additional losses to the facility due to cars coming off lease and staying off lease for longer periods. In short, the facility loses money if a tank car is brought in too frequently.
It is therefore evident that there is a need for some form of highly detailed inspection system to increase the interval between required inspections and reduce overall inspection costs.